We are proposing a multi-year conference grant which seeks to establish forum for researcher to pursue collaborative studies of the molecular genetics of attention deficit hyperactivity disorder (ADHD). This application was conceived in response to a recent call from the NIMH for researchers to establish mechanisms for pooling molecular genetic and clinical data in a manner that would facilitate the detection of genes predisposing to psychiatric disorders. Although these preliminary results are encouraging, several considerations suggest that fully clarifying the genetic architecture of ADHD will require large samples. The field's experience with studies of schizophrenia and bipolar disorder show that the sample sizes collected by individual investigators can provide evidence for linkage but are not sufficient to clone disease genes. This is consistent with statistical considerations regarding the power to locate genes and the likely genetic complexity of psychiatric disorders. These considerations suggest that coordinated collaboration among investigators is needed to share findings and pool samples. The main aim of the proposed conference grant is to overcome the hurdles to collaboration by establishing yearly conferences among investigators studying the genetics of ADHD. These conferences win be held in conjunction with the annual meeting of the International Society of Psychiatric Genetics. The main goal of the conference is to establish a network of investigators who are studying or plan to study the molecular genetics of ADHD. Subgoals of these conferences are: 1. To standardize data collection methods across sites to facilitate pooling of diagnostic data.: 2. To facilitate joint submissions of large collaborative projects.; 3. To standardize DNA marker sets across sites to facilitate the pooling of genotypic data.: 4. To create a mechanism for pooling samples so that potential findings from one group can be cross-validated on the pooled data from the remaining groups.; 5. To establish rules for sharing genotypes and DNA across sites that will preserve the academic independence of each site and foster junior investigators while allowing for the pooled analysis and publication of data.; 6. To encourage women and minorities to pursue molecular genetic studies of ADHD. There are three reasons why the field needs a series of conferences to foster collaborative studies of the molecular genetics of ADHD: 1) family, twin and adoption studies show that much of the susceptibility to ADHD is mediated by genes. Hence, molecular genetic studies are justified; 2) ADHD is likely to have a complex genetic etiology which includes multiple genes that act in an additive or interactive fashion and 3) no such meeting has ever own held. Statistical considerations indicate that no one investigator is likely to have access to a sample that is sufficient to detect and clone disease genes.